Study On GIFT Tilapia Cultured With Non-situ Biofloc Technology

Only about 20%-30% of the feed protein was transformed by adults, most can not be used and left in aquaculture water. According to heterotrophic bacteria growth metabolic demand characteristics, researchers propose the aquaculture of C: N ratio increased to more than 10, to promote aquaculture heterotrophic bacterial assimilation ammonia nitrogen and growth advantage form microbial flocs(Biofloc), and to control the accumulation of ammonia nitrogen in aquaculture water. The conventional biological flocculation method is the direct culture of biological flocculation in the culture pond(tank), which can be called in situ biological flocculation.But relatively few applications of production scale, the main reason is that the stability of the system is not easy to control.In view of the above problems is proposed in this paper biological flocculation farming methods in non-situ, the key solution of stability and controllability of the bioflocculation aquaculture of tilapia, reduce the interference of breeding object, experimental design the in situ group served as the control group, the non-situ group as experimental group. The experimental group according to different hydraulic retention time(HRT) divided into non-situ group 2h group, 4h group, 6h group and experimental content divided into the following three parts:1、Study on the water quality and the flocculation of the culture in non-situ biological flocculation systemIn situ and non-situ groups of three forms of nitrogen and total nitrogen change trend broadly consistent. Thirty-third days in situ group and non-situ group in the ammonia nitrogen concentration reached the peak, respectively, reaching 11.85±2.20mg/L、8.02±5.64 mg/L、9.78±4.12 mg/L、8.31±2.42 mg/L. After 56 days, the concentration of ammonia nitrogen was basically stable below 3 mg/L. Nitriteconcentration in 37 days to reach the peak, respectively, reached 12.33±1.85 mg/L、8.43±4.82 mg/L、5.38±5.95 mg/L、6.98±4.58 mg/L. On the 53 day after the concentration of nitrite is basically stable below 2mg/l. First month of flocs crude protein content was 30%, reached to 40% in the second month, growing generated in the breeding process of flocs crude protein content, crude protein content of the late respectively 36.56±1.01 %、41.69±3.83 %、42.58±1.30 %、38.10±1.27 %.Throughout the experimental process, the coarse ash content of all groups in the continuous growth, in situ group of crude ash content was significantly higher than in the second months after the non-situ group. At the end of the experiment, the results were 31.01±0.11 %、29.47±0.68 %、25.27±0.15 %、26.17±0.25 %.2、Study on growth status and nitrogen balance of cultured tilapia in non-situ biological flocculation systemGroup in non-situ at the end of the average body weight anf the breeding density is significantly higher than that in situ, each group of experimental fish as final weight size were non-situ 4h group > non-situ 6h group > non-situ 2h group > situ group. The non-situ 4h group breeding density reached feed coefficient of 37.99±2.34 kg/m3. Each group had no significant difference(P > 0.05). The survival rate of the experimental fish was higher, initial fatness is no difference in the circumstances, at the end of experiment group of non-situ fatness was significantly higher than that of in situ group. In the whole process of the whole culture, the content of crude protein in the muscle of the group was higher than that of the non-situ group, and the total protein content of the whole fish was consistent.The nitrogen in each group were 4801.01±119.33 g、4878.90±337.68 g、5450.17±334.99 g、5147.08±235.62 g, accounting for 59.87±1.49 %、61.10±4.32 %、67.64±4.16 %、64.17±2.94 %.3、 Study on the digestive and immune system of the culture in non-situ biological flocculation systemChange tendency of in situ and non-situ each fish pepsin activity is the same are decreased in the first three months, rising in the first four months, at the end of the experiment, each group of pepsin activity to less than initial activity. In situ and non-situ groups of gastric lipase and intestinal lipase vitality are showing a trend of increased first and then decreased, the second month activity reached the highest. Meanwhile, we tested the various biochemical indexes of blood in which in situ and non-situ groupsAKP in the whole experiment process has been in decline groups declined slowly to24.67±3.06 IU/L、20.67±3.79 IU/L、23.67±5.13 IU/L and 25.00±8.54 IU/L. Which non-situ each AST in the whole experiment process has been in decline groups fell to14.67 ± 4.51 IU/L 、 16.67 ± 0.58 IU/L and 12.67 ± 0.58 IU/L in situ plasma AST activity.At the end of the experiment, the activity of AST still have 58.00±18.25 IU/L,and non-situ between groups difference significant.In total cholesterol and triglycerides in the experimental is increased.